Inhibitory effect of molybdenum and vanadium salts on aflatoxin B1 synthesis by Aspergillus flavus

Abstract
The effects of Zn, Mg, Fe, Cu, Mo and V, added in various salt forms, on mycelial weights and aflatoxin B1 accumulation in the mycelium of A. flavus were investigated in liquid shake cultures. Ammonium heptamolybdate, when added to a complete medium at concentrations of 50-100 mg/l, reduced aflatoxin B1 accumulation without affecting growth of the fungus. Na2MoO4 and NaVO3 also reduced aflatoxin B1 yields without affecting mycelial growth, but to a lesser extent. The addition of ZnSO4 stimulated aflatoxin B1 production in all media. The influence of the other trace elements on aflatoxin production depended on the level of trace elements present in the basal medium. MnCl2 had a stimulatory effect; CuSO4 depressed yields. Mycelial levels of aflatoxin had peaked and then declined before mycelial dry weights had reached maximum. High yields of aflatoxin B1 were obtained in media having a final pH as low as pH 2.8.